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Full exposure: An oncologist’s perspective on sunscreen

July 24, 2014

We all have risk factors for cancer. Some of us smoke, some of us drink too much and some eat too many processed foods. Me? I love the sun. I love to sit outside and feel the warmth on my skin. I tell myself it’s not such a bad habit. I wear sunscreen. That prevents skin cancer, right?

Interestingly, the medical science behind sunscreen is not all that conclusive. For those of you who’ve been slathering it on this summer, I wanted to review some facts about skin cancer and whether sunscreen can prevent it.

Doctors divide skin cancer into two categories: melanoma and non-melanoma. Non-melanoma skin cancers include basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). BCC and SCC account for at least 80 percent of all skin cancers.i Melanoma is less common but more serious. If left untreated, it’s much more likely to spread than other forms of skin cancer. While sun exposure is a risk factor, melanoma also depends on genetics, race and environmental factors.ii

Only one randomized-controlled trial has studied the effect of sunscreen on skin cancer rates: the Nambour Trial conducted in Queensland, Australia, in 1992.iii Queensland gets a lot of sunshine and has the highest known rates of skin cancer. For the study, more than 1,600 people were randomly divided into two groups and followed for almost five years. Those in the “daily sunscreen group” had to use sunscreen of SPF 16 daily, while those in the “non-screen group” used sunscreen at their discretion.

The trial found no significant reduction in basal cell carcinoma rates with the use of sunscreen. Incidence of squamous cell carcinoma, though, dropped 40 percent. What about melanoma? Eleven people in the daily sunscreen group were diagnosed with invasive melanoma, as were 22 people among the non-sunscreen users. For this reason, some researches quote a 50 percent reduction in melanoma (from 22 to 11 people) due to sunscreen.iv

Interestingly, when the researchers looked at melanomas occurring where sunscreen was applied—on the head, neck, arms and hands—there was not a significant reduction. Still, the 50 percent statistic has fueled the commonly held view that sunscreen prevents skin cancer. Yet other non-randomized studies show no conclusive data on the benefit of sunscreens on melanoma and basal cell carcinoma.v

What are the benefits of sunscreen?

Reduces wrinkles: Skin aging was 24 percent less in the daily sunscreen group in the Nambour Trialvi

Reduces the incidence of SCC

Reduced the incidence of melanomas: From 22 to 11 people in the Nambour Trial

Some animal studies indicate that sunscreen could disrupt hormone levels.

There is no human data on toxicity. However, the skin rapidly absorbs sunscreen. Some researchers worry that sunscreen could harm pregnant women and children.viii

My recommendation is to avoid getting sunburned. Here’s how:

Try to avoid sun tanning in the summer during the afternoon hours. If you must be outside in the hot sun, wear a long-sleeved shirt, long pants and a hat. The science behind protective clothing is much better than that of sunscreen.

Wear sunscreen as needed to avoid sunburn. If you do put it on, shower before you go to bed to remove the chemicals from your skin.

Avoid spray sunscreens. While these sprays are easy to apply, you risk inhaling chemicals into the lungs, where they can be absorbed more rapidly than the skin.

Finally, it’s not necessary to avoid the sun. I do not recommend wearing makeup with sunscreen every day. Modest sun exposure is essential. Vitamin D deficiency is a common health issue, and the best way for your body to make vitamin D is through sun exposure.ix